Walker, Halliday & Resnick — Coulomb's Law: Problem 25

25 In Fig. 21-18, particles 2 and 4, of charge $-e$, are fixed in place on a y axis, at $y_2 = -10.0 \text{ cm}$ and $y_4 = 5.00 \text{ cm}$. Particles 1 and 3, of charge $-e$, can be moved along the x axis. Particle 5, of charge $+e$, is fixed at the origin. Initially particle 1 is at $x_1 = -10.0 \text{ cm}$ and particle 3 is at $x_3 = 10.0 \text{ cm}$. (a) To what x value must particle 1 be moved to rotate the direction of the net electric force $\vec{F}_{\text{net}}$ on particle 5 by $60^\circ$ counterclockwise? (b) With particle 1 fixed at its new position, to what x value must you move particle 3 to rotate $\vec{F}_{\text{net}}$ back to its original direction?